In multicast and broadcast applications, data are transmitted from a server to multiple receivers over wired and/or wireless networks. A multicast system as used herein is a system in which a server transmits the same data to multiple receivers simultaneously, where the receivers form a subset of all the receivers up to and including all of the receivers. A broadcast system is a system in which a server transmits the same data to all of the receivers simultaneously. That is, a multicast system by definition can include a broadcast system.
Consider multicast (downlink) and multi-access (uplink) channels with one access point (AP) and several nodes. In the IEEE 802.11n draft standard, a reverse direction (RD) protocol is introduced for fast scheduling of bidirectional traffic flows within a transmission opportunity (TXOP). The reverse direction protocol permits (allows) the node, which has obtained the TXOP to grant reverse directional transmissions to another node while it is still in control of the TXOP. If the channel conditions between the nodes are inadequate (poor) then transmissions between the two nodes suffers. That suffering may be reduced data rate and/or throughput.
In the IEEE 802.11n draft standard, reverse direction (RD) protocol has been proposed as in FIG. 1. The reverse direction protocol of the IEEE 802.11n draft standard only schedules bidirectional transmission between two nodes. There is no existing scheduling protocol for three-node bidirectional transmissions in IEEE 802.11 WLAN standards.
It would be advantageous to have a third node act as a relay node for the two nodes. The use of such a third (relay) node, however, complicates the communications (transmissions) between the two nodes.